Dual atomization and electrostatic deposition means



Sept. 19, 1961 J. SEDLACSIK, JR

DUAL ATOMIZATION AND ELECTROSTATIC DEPOSITION MEANS Filed' Dec. 8, 1959 Fig@ " WMM lNvr-:N'roR JOHN SEDLACSIK JR.

BY /A/If etary Research & Development Corp., Garfield, NJ.,

a corporation of New Jersey Filed Dec. 8, 1959, Ser. No. 858,146 4 Claims. (Cl. 239-15) My invention relates to an apparatus for electrostatic coating with liquid coating materials such as paints or the like, and is a continuation-in-part of abandoned application Serial Number 607,825.

In particular, it relates to new and useful improvements in the apparatus used in the atornizat-ion of materials which are then precipitated, at least in part, electrostatically, upon the surface of an article to be coated.

In utilizing this invention, the surface of the article to be coated and the atomizer head are brought into spaced relationship and an electrical potential difference is established therebetween for creating an electrostatic field for charging the particles to be electrostati'cally deposited on said articles.

One feature of the invention is to provide a centrifugal atomizer for mechanically feeding a tilm of fluent material, such as paint, outwardly toward the peripheral edge or atomizing edge of the device.

A novel feature of the invention is to employ a stationary spray nozzle disposed axially in the atomizer and having its atomizing end rearwardly of the peripheral edge of the atomizer. The nozzle is adjustable, so that a spray may be provided all about the axis thereof, to provide a 360 spray. The material is urged under pressure out toward the atomizing end of the nozzle forming a 360 coating material feeding pattern, which is positioned externally of a cylindrical channel, which is coupled to a source of compressed air. The paint is urged outwardly of its cylindrical feeding chamber adjacent a flat surface, while the annular ring of air internally of the circular paint source is directed outwardly to atomize the paint and drive it laterally of the nozzle head axis. An outer sleeve or spray control is movable longitudinally of the axis of the nozzle to direct the lateral spray either forwardly or rearwardly within the reservoir of the atomizer to control the density of the spray immediately adjacent the inner surface of the centrifugal atomizer and depositing same thereon.

One of the advantages is to provide a pneumatic 360 spray for pneumatically atomizing a coating material, which is projected sidewise onto the internal surfaces of an annular cone or atomizer disc. In this manner, the paint will be initially atomized in a 360 radially expanding spray, which, thereafter, forms a film on the inner surface of the atomizer, where centrifugal action urges the film of coating material outwardly toward the atomizing edge.

The nozzle -atomizer has means for directing the spray forwardly or rearwardly within the contines of the reservoir of the atomizer.

Coating material on the atomizer or applicator head is induced to leave the head and reservoir under the inuence of the centrifugal, force and potential difference as a finely dispersed spray of liquid particles, which particles are then deposited on the surface of the article to be coated, so as to form the desired decorative or protective coating.

By virtue of this apparatus, the dual atomization produced 4in a continuous sequence provides coatings which may be applied with greater efficiency and improved uniformity. f

Additionally, the coating operation can be performed in a smaller area of space with a reduced amount of apaired States Patent O paratus and at an increased rate of speed, as compared with known prior art devices.

Electrostatic atomization, as applied in spray coating, has many advantages. It greatly increases the efficient use of coating material. It eliminates the necessity of ventilation. It permits the use of simplitied apparatus.

Herein is provided an apparatus, which includes an atomizer in the form of a cone-shaped chambered structure `or reservoir, which may be rotated, if desired. An extended `discharge edge is associated with the outer or atornizing edge or exit end of the atomizer chamber. An electrical potential coupled to the atomizer raises the discharge edge to a potential high enough to cause the electrostatic breaking up or atomization of the liquid material supplied to it.

The atomizing peripheral discharge edge is preferably made of electrical conducting materialA and is of knifeedge sharpness yin its cross-section. The extent of the discharge surface may be rectilinear, arcuate or annular, although I have found that optimum results are achieved by using a discharge edge in the form of an annulus. Such an `annular edge, under the action of an electrostatic iield, permits the points of atomization to distribute themselves uniformly therearound. Such is due to the mutual electrical repulsion of the several points or streams of atomization.

The use of the invention may be carried out by presenting, in a predetermined position, the leading edge of a thin stream of liquid material and moving an article past this leading edge and in spaced relation thereto. The liquid may be under 4atmospheric pressure or it may be subjected to greater pressures through the use of atomized air. That is, the liquid and air may be used in combination.

The electrical potential and the liquid and air pressures may be adjusted for varying the quality of atomization of the liquid material from the leading edge.

The invention resides in the particular arrangement, construction, and the relationship of the various elements of spray coating device, as is disclosed in the accompanying specification, in which the above stated and other objects of the invention will be apparent.

-In the drawings:

FIG. l is a side view, partially broken away, of the yatomizer arrangement operatively coupled to la gun portion to provide atomization of coating material;

FIG. 2 is a longitudinal sectional view of the centrifugal aperture and nozzle atomizers operatively coupled to prow'de passages for uid therethrough;

FIG. 3 is a sectional view taken along lines 3-3 of FIG. 2, showing passages for coating material and compressed `air;

FIG. 4 is a sectional view taken along lines 4-4 of FIG. 2, showing the several chambers for the paint and air;

FIG. 5 is a representative view of a system showing the high voltage coupled to ground and the atomizer arrangement having the electrostatic field between the atomizer arrangement and the larticle to be coated, which article is carried by a representative conveyor coupled to ground; and

FIG. 6 is a vertical sectional view of portions of the annular rims in relation to the lip of the nozzle atomizer to show directional spray control.

Referring now to the drawings, there is shown one form of the invention, which includes an atomizer structure generally indicated by 10 `in the form o-f a cone having an inner surface 12 lfor forming a thin film supply of liquid coating material. The surfaces of the atomizer 10 are shaped to eliminate all unnecessary corners or points, and therefby to increase the eciency of the action of the electrostatic forces on the liquid coating material, where the S entire reservoir structure is made of electrical conducting material.

At least, at its extreme outer end, the reservoir wall is of conducting material and is formed to provide an annular discharge edge 14, which is of knife-edge sharpness or is otherwise attenuated.

The wall portions of the structure are machined to a smooth surface, so as to offer `a uniform passage along the entire length thereof, which passage functions to aid in the control of the feeding of liquid material to the discharge edge `in substantially equal quantities along its entire periphery.

For reasons, as will hereafter be made more apparent, the discharge edge must be smooth and free from any abrupt changes in direction, in order that the potential gradient of the iield will be as uniform as possible.

As compared with the knife-like discharge or atomizer edge 14, the body wall is tapered, as shown, so that the inner end of the inner surface 12 is of considerably less diameter than the diameter at the annular discharge or `atomizer edge 14. Such arrangement permits the body wall to be tapered so that the inner end portion 16 thereof is the thickest portion of the structure, whereby a sturdier structure is provided. However, a uniform thickness of material may be rused.

A bushing 2G may be provided to insure a tight iit hetween the atomizer l@ and outer sleeve 18.

In use, the coating material and the air are delivered to the inner surface 12 through the 360 nozzle atomizer 19 at the outer end of the outer sleeve 18. The `materials are thus circumferentially distributed about the interior of the atomizer cone 10, ffrom which they flow to the extended annular atomizing edge 14.

A high potential source 22, of direct current, has one side thereof connected to ground, as shown by the conventional symbol, and the other side connected by a conductor 26 to a terminal connected to the metallic nose piece '3S to one end of the supporting structure 40. The supporting structure has a tail piece 42 connected to sources of air and paint 44 and 46, respectively, all of which are operatively coupled to provide air and paint to the atomizer, as depicted in FIGS. 2, 3 and 4.

If the entire structure, except for the portion comprising the discharge or atomizing edge, is made of electrical insulating material, then the potential source 22 may be connected directly to the portion of the structure which comprises the discharge edge.

When the discharge atomizing edge 14 is charged to the desired electrical potential, and liquid with or without air combined therewith is supplied to it, the apparatus just described will atomize and electrostatically deposit such liquid. A pattern obtained by disposing the atomized material on a iiat sheet immediately in front of the device, is in the outline of an annular ring. Obviously, the pattern may be modiiied by varying the diameter of the edge 14.

One means for controlling the rate of ow of liquid material through the passage in atomizer 1t) is by varying the rate of flow through the nozzle spray head. That is, the rate of flow of coating material to the discharge edge may be controlled by adjusting the pressure applied to the liquid material in the chamber by appropriate means in the nozzle spray head.

The coating material `lrn on the atomizer is centrifugally thrown radially outward, along the plane of the atomizer edge. r[The atomizer material will follow the lines of force of the eld in being precipitated upon the surface of the article to ibe coated. When precipitated on a flat surface, the atomized material appears in the form or pattern of a hollow ring. Relative motion ofthe article being coated in this field pattern results in a complete and uniform coating,

The material is centrifugaily atomized lby a `discatomizer from a series of points or locations circumferentially about the atomizing edge of the atomizer, which points, by mutual electrical repulsion or centrifugal action, will assume and remain in a series of relatively equally spaced positions.

The cone-shaped atomizer 10 may, if desired, be rotated with the applicator head during the coating operation. When the atomizer is rotated, the uniformity of the coating obtained is greatly improved, 'because the coating material is distributed more uniformly about the interior of the atomizer and the annular extended discharge atomizing edge, and thus, is centrifugally atomized more uniformly into a pattern issuing from such `atomizing edge. Without rotation, the coating material would flow to the lower portions of the cone under the action of gravity, and the pattern which would result, when such a device was used for coating vertically disposed surfaces, would be asymmetrical to such an extent that the lower half of the surface would receive practically all of the coating.

Annular gear 30, surrounding the spray gun head, is adapted to aid in the rotation of the atomizer 10 as desired, said gear 30 being a driven gear in mesh with a driving gear, which is driven by the shaft 32 of a motor 64 in the conventional manner.

The spraying device itself, considered in more detail, utilizes thel technique of dual atomization by mechanical means, and wherein one mechanical means embraces a pneumatic spray for mixing two iluids, such as a coating `material and air under pressure. lFurther, high voltage may be applied for establishing an electrostatic field in the area of the device for charging the particles of coating material to facilitate dispersion and disposition of said coating material onto articles to be coated.

The spray device per se consists of a gun portion 50, comprising the nose and tail pieces 38 `and 42 for coupling to the nozzle arrangement, consisting of the centrifugal atomizer 10 and the nozzle atomizer 19, mounted on the end of the gun portion and coupled thereto by an air cap 52, which employs a threaded arrangement for holding the atomizer arrangement 54 in a detachable arrangement with the gun portion 50 to permit interchangeability of atomizer arrangements on the gun portion.

The arrangement 54 comprises a centrifugal atomizer 10 rotatably mounted about a nozzle atomizer 19 and mounted on the gun portion 50 by the knurled air cap 52. The nozzle atomizer 19 has an outer sleeve, which is adjustable and can be used as a spray control of the nozzle atomizer. The body 55 of the nozzle atomizer has a shoulder 56 on the base portion, which engages the flange 57 of the air cap 52 which has a threaded portion, which is complemental to a threaded portion of the neck 58 of the gun portion 50 to permit the nozzle arrangement to be interchanged with the other nozzle arrangement. lThe ybody `55 has a central aperture 59 therein, which extends therethrough and has the inner end thereof engaging the conical tip 60 of the paint valve 61. The tip 60 ts tightly against the opening in the central aperture 59 and when the coating material or paint is forced under pressure into the tip 60, it merges into a small opening in the tip nozzle to ll the central aperture 59 to be fed outwardly into the nozzle atomizer. The body 55 is threadedly connected to the outer sleeve 18 at the inner end thereof, with the outer sleeve 18 having a tapered portion on the free end thereof and being hollow to receive the body 55 and the inner sleeve 62. The inner sleeve 62 has a central aperture therein and is threadedly connected to the outer end of the body 55 to permit paint to flow therethrough. The outer end of the inner sleeve 62 has a sleeve portion 63, which terminates in an annular rim 64. The recessed shoulder 65 has an annular recess 66 therein to receive an O ring 67, which has a tight lit with the inner surface of the sleeve 18 to prevent air from passing therebetween. A plurality of diagonal air channels 68 communicate from the chamber y69 to form, between the sleeve and the body, an inner vsleeve to receive air through the passage 70, which communicates with the air cap 52 on the end of piece 38 and to the air supply 44.

The nose chamber 71 is formed between the sleeve portion 63 and the tapered portion of the outer sleeve 18 and paint if fed therein by the paint channel 73, which communicates from the central aperture 59 fed from the tip 60. A dispersion tip 75 has an annular lip 76 on the end of an annular body 77 which has a stem 80 tightly fitted into the outer end of the central aperture -9 and centrally disposed therein to permit a passage between the sleeve portion 63 and the body 77 of the nozzle atomizer 19, whereby air fed through the air channels 68, form an annular curtain of air directed outwardly to impinge the under side of the lip 76 of the dispersion tip 75 and deect the air normally in a radial pattern normal to the axis of the atomizer. The tapered end of the sleeve 18, which is threadedly connected to the body 55, is adjustable to move longitudinally toward or away from the lip 76 of the dispersion tip so that the sleeve rim 83 of the nose the sleeve, will form an annular rim, which may be,

moved longitudinally so that the plane of the sleeve 83 may be moved axially in one direction or the other in relation to the annular rim 64.

The coating material or paint which flows through the paint channel 73, will ow into the nose cham-ber 71 and out over the rim 83 in normal operation.

Under the influence of the air moving in the space between the sleeve portion 63 and the body 77, the air will be moved toward the lip and deflected tangentially at right angles to the nozzle axis in the direction of the arrow Y. With the rim as shown in FIG. 6, there will be provided a 360 spray substantially .in a radial pattern, as shown in FIG. l, with the paint being directed substantially normal with the axis of the device. By moving the nozzle forward to the position shown dotted as at 88, the spray will be deflected axially forward at an angle in relation to its axis, and when the sleeve is moved rearwardly of that shown, a slight amount, the paint will be deflected rearwardly of the plane indicated by the arrows X, X in FIG. l. The arrows X, X, in FIG. l, show the path of the particles which are thrown substantially normal to the axis of the device under the influence of centrifugal force when the centrifugal atomizer is rotating at a suitable speed for centrifugal atomization.

A bronze bearing 90 is secured to the inner cylinder in the bore of the centrifugal atomizer 10 and has a pressfit therewith to hold same in position. The bronze bearing 90 rotatably slides on the outer surface of the outer sleeve 18 and is held in position by cone bearing locators 91 and 92 which are adjustable by screws as shown.

-In operation, the paint which moved through the nozzle will ow over the sleeve rim 83 and into the path of the air, which is deflected outwardly as it moves from the cylindrical curtain of air and impinges the body and lip of the dispersion tip 75. The adjustment of the outer sleeve 18 permits the pneumatic spray to provide a 360 spray, which is adjustable to spray either normal to the axis of the device or to be adjusted for directing the spray forwardly or rearwardly, as may be desired, so that there is complete pneumatic atomization of the spray particles, which impinge the inner surface of the centrifugal atomizer 10. Under the action of centrifugal force, due to rotation of the atomizer 10, the spray from the nozzle forms a lm upon the inner surface of the centrifugal atomizer and this lm is driven uniformly outwardly toward the atomizer edge 14, from whence it is thrown tangentiaily in the direction of the arrows X, X, which provide a normal flat centrifugally produced spray. When the high voltage source, such as 22, is connected, as is shown in FIG. 5, to the device, an electrostatic field 93 is established between the atomizer arrangement and the representative article 94 to be coated. The electrostatically charged particles, because of their mutual repulsion toward each other, will create the well known conventional dispersion of the particles and provide Wrap-around -action and general deposition of the charged coating material onto the surface of the article to be coated in a well known manner.

In FIGS. 3 and 4, the various channels and passages are shown as set forth above.

In FIG. 3, the aperture is shown and is merely indicated in the tip 60 as communicating with the opening of the paint valve 61 which feeds the coating material into the central aperture 59.

As the articles on the conveyor approach the device, electrical potential is applied to the device and the liquid coating material is supplied to the discharge edge. At this approaching position, the articles are sprayed with a mist coat of atomized material from the device. As the articles move directly in front of or under this device, a heavier spray of atomized material is applied to the article. As the articles move beyond the device, the amount of material applied to them gradually decreases until they move out of the coating zone. At this time, the articles are completely coated.

It will be noted that all the atornizing structure above described, provides for ow of liquid material to the discharge edge in the form of a iilm. The form of such film follows the form of the discharge edge and may be annular, arcuate, rectilinear, or of any other desired shape; but in each instance the film, at least at the discharge edge, is of substantially uniform thickness and of many times this thickness in the other transverse dimensions.

By this invention, superior atomiziation of liquids is obtained and it is possible to disperse the atomized liquid material over extended areas with improved uniformity. The patterns of the deposited liquid material may be varied in many ways to facilitate coating articles of many different shapes and sizes. It will thus be seen that there has been provided by this invention an apparatus in which the various objects hereinbefore set forth are successfully achieved.

While the specific embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. An atomizer arrangement for sequentially producing dual atomization and electrostatic deposition of coating material onto an article to be coated comprising, a

pressure operated nozzle for initially atornizing fluid coat-V ing material into fine particles and spraying a pattern of said coating material particles substantially radially of the axis of said nozzle, a centrifugal atomizer revolubly mounted relative to said pressure operated nozzle and positioned to receive substantially all of the spray emitted from said pressure operated nozzle on an inner surface of said centrifugal atomizer, means for rotating said centrifugal atomizer at a speed sufcient to finally atomize and project the particles laterally from said centrifugal atomizer, and means for establishing an electrostatic field adjacent said centrifugal atomizer for charging the particles emitted therefrom to facilitate electrostatic deposition, said pressure operated nozzle including adjustable spray control means for controlling the density of the spray adjacent the centrifugal atomizer and deposition onto the inner surface thereof. f

2. An atomizer arrangement for sequentially producing dual atomization and electrostatic deposition of coating material onto an article to be coated comprising, a pressure operated nozzle for initially atomizing fluid coating material into fine particles and spraying a pattern of said coating material particles substantially radially of the axis of said nozzle, a centrifugal atomizer revolubly mounted relative to said pressure operated nozzle and positioned to receive substantially all of the spray emitted from said pressure operated nozzle on an inner surface of said centrifugal atomizer, means for rotating said centrifugal atomizer at a speed suicient to finally atomize and project the particles laterally from said centrifugal atomizer, and means for establishing an electrostatic field adjacent said centrifugal atomizer for charging the particles emitted therefrom to facilitate electrostatic deposition, Said pressure operated nozzle having an annular material discharge opening to provide a 360u substantially radial spray pattern and including adjustable means for controlling the direction of the lateral projection of said 360 radial spray pattern.

3. An atomizer arrangement for sequentially producing dual atomization and electrostatic deposition of coating material onto an article to be coated comprising, atomizing means for initially atomizing fluid coating material into line particles and establishing substantially a 360 spray pattern of said coating material particles radially of the axis of said atomizing means, a centrifugal atomizer revolubly mounted and disposed relative to said atomizing means to receive substantially all of the spray emitted from said atomizing means on an inner surface of said centrifugal atomizer, means for rotating said centrifugal atomizer at a speed sufiicient to finally atomize and project the particles of coating material laterally from said centrifugal atomizer, and means for establishing an electrostatic field adjacent said centrifugal atomizer for charging the particles emitted therefrom to facilitate electrostatic deposition of the particles onto the surface of an article to be coated, said `initial atomizing means including spray control surfaces for controlling the density of the'spray adjacent the centrifugal atomizer and deposition onto the inner surface thereof.

4. An atomizer arrangement for sequentially producing dual atomization and electrostatic deposition of coating material onto an article to be coated comprising, nozzle means for initially atomizing fluid coating material into ne particles and spraying a pattern of said coating material particles substantially radially of the axis of said nozzle means, a cone type centrifugal atomizer revolubly mounted and positioned relative to said nozzle means to receive substantially all of the spray emitted from said nozzle means on an inner surface of said centrifugal atomizer, means for rotating said centrifugal atomizer at a speed sufficient to finally atomize and project the particles laterally from said centrifugal atomizer, and means for establishing an electrostatic eld adjacent said centrifugal atomizer for charging the particles emitted therefrom to facilitate electrostatic deposition, said nozzle means for initially atomizing the coating material having 2&Sdurfaces establishing a radial and substantially uninter- "fupted spray pattern of 360 for controlling the dispersion characteristics of the 360 spray pattern.

References Cited in the file of this patent 62,564 France Jan. 26, 1955 

